The present invention relates to combustion knock control in an internal combustion engine, and particularly to combustion knock control in a two-cylinder, V-twin, air-cooled motorcycle engine.
In the ideal condition, combustion in an engine""s combustion chamber propagates from the spark plug through the combustible mixture along a controlled combustion wave. Knock occurs when spontaneous combustion happens ahead of the combustion wave, resulting in power loss for the engine. Knock is produced by spontaneous combustion or autoignition. Knock occurs when the local pressure and heat within the combustion chamber is above the requisite local pressure and heat required for spontaneous combustion.
It is known to control knock in a four-cylinder, water-cooled automobile engine. One method entails obtaining an ion signal representative of ionization across the spark gap of a spark plug. After obtaining the ion signal, a controller detects whether knock is present within the combustion chamber. If the controller detects knock, then the controller will vary the timing of the spark event. However, prior art two-cylinder, air-cooled motorcycle engines did not control knock within the engine, and were forced to accept the resulting loss of power. One reason for this is that prior art motorcycles did not have the necessary control and processing power required to implement knock control.
One of the problems with two-cylinder, air-cooled engines (e.g., motorcycle engines) is that the engines run much hotter than water-cooled engines (e.g., automobile engines). The most obvious reason for this is that water-cooled engines use a coolant for promoting heat removal, whereas air-cooled engines rely substantially on air-flow for heat removal. This problem is intensified if the motorcycle is running in warm surroundings. The increased running temperature of the motorcycle engine results in an increased peak pressure within the combustion chamber and, consequently, the motorcycle engine is more susceptible to knock.
A second problem that arises with two-cylinder, air-cooled motorcycle engines is that air-cooled engines have a larger engine temperature range than water-cooled engines. That is, because air-cooled engines do not contain a liquid coolant, the engine temperature varies over a larger temperature range than water-cooled engines. Due to the larger temperature range, it is more difficult to calibrate against or control engine knock. Even further, a large number of motorcycle engines, are calibrated close to the knock limit. These motorcycle engines are calibrated at peak pressure because that is the point where the most amount of output power for the engine results. In normal ambient conditions this does not result in a problem. But at elevated temperatures, knock can be an issue.
Knock is even more prevalent in two-cylinder, V-twin, air-cooled motorcycle engines having one cylinder positioned in front of the other. In such an engine engine, the rear cylinder typically runs hotter than the front cylinder because the rear cylinder receives less airflow then the front cylinder. The increased temperature for the rear cylinder results in the rear cylinder being more susceptible to knock than the front cylinder. Therefore, it would be beneficial to create a controller for performing knock control in a two-cylinder, V-twin, air-cooled motorcycle engine.
The invention provides a motorcycle including a frame, front and rear wheels coupled to the frame for rotation with respect to the frame, and a two-cylinder engine mounted to the frame. The engine includes a housing, a crankshaft mounted for rotation within the housing, first and second cylinders having first and second combustion chambers, respectively, and first and second pistons reciprocating in the first and second cylinders, respectively. The engine of the motorcycle is preferably a two-cylinder, V-twin, air-cooled engine having one cylinder positioned in front of the other. The motorcycle further includes a spark generating circuit including a spark plug having a spark gap exposed to the first combustion chamber. The spark generating circuit produces a spark across the spark gap in response to a sparking signal. The motorcycle further includes an ion signal circuit that provides an ion signal indicative of an ion current being generated across the spark gap. The motorcycle further includes an analysis module electrically connected to the ion signal circuit and the spark generating circuit. The analysis module generates the sparking signal in a timed sequence, receives the ion signal from the ion signal generating circuit, measures a knock intensity within the ion signal, and modifies the timing sequence in response to an indication of knock in the first cylinder.
The motorcycle can further include a fuel injector having a fuel injector circuit. The fuel injector provides an amount of fuel to the combustion chamber in response to a fuel injector signal being provided to the fuel injector circuit. The fuel injector circuit is electrically connected to the analysis module. The analysis module generates the fuel injector signal and modifies the fuel injector signal in response to an indication of knock within the first cylinder.
The motorcycle further includes a second spark generating circuit substantially identical to the first spark generating circuit and a second ion signal circuit for use with the second cylinder. The analysis module is electrically connected to the second ion signal circuit and the second spark generating circuit and functions as described above to modify the second timing sequence. The provision of a second circuit facilitates separate control of the first and second cylinders.
The analysis module includes a low-pass filter. The low-pass filter receives the ion-signal from the ion signal generating circuit and passes a low-pass signal having low frequencies. The analysis module further includes a band-pass filter having a frequency range. The band-pass filter receives the low-pass signal from the low-pass filter and passes a band-pass signal having frequencies within the frequency range. The analysis module further includes an integrator that receives the band-pass signal and provides an integrated signal indicating an amount of knock energy in the band-pass signal. The analysis module further includes a microprocessor electrically connected to the integrator. The microprocessor receives the integrated signal and implements a software program for determining whether the integrated signal represents knock being present within the cylinder.
The invention further provides a motorcycle including a frame, front and rear wheels coupled to the frame for rotation with respect to the frame, and a two-cylinder, V-twin, air-cooled engine mounted to the frame. The engine includes a housing, a crankshaft mounted for rotation within the housing, first and second cylinders having first and second combustion chambers, respectively, and first and second pistons reciprocating in the first and second cylinders, respectively. The motorcycle further includes a spark generating circuit including a spark plug having a spark gap exposed to the first combustion chamber. The spark generating circuit produces a spark across the spark gap in response to a sparking signal. The motorcycle further includes an ion signal circuit that generates an ion signal indicative of an ion current being generated across the spark gap. The motorcycle further includes a conditioning chip that receives the ion signal and generates a knock intensity signal. The motorcycle further includes a processor and software for operating the processor to provide a sparking signal at a timed sequence, to determine whether the knock intensity signal represents knock within the first cylinder, and to modify the timed sequence in response to an indication of knock in the first cylinder.
The invention further provides a method of varying a spark event in a two-cylinder engine of a motorcycle. The method includes the act of providing a motorcycle including a frame, front and rear wheels coupled to the frame for rotation with respect to the frame, and a two-cylinder engine mounted to the frame. The engine includes a housing, a crankshaft mounted for rotation within the housing, first and second cylinders having first and second combustion chambers, respectively, and first and second pistons reciprocating in the first and second cylinder, respectively. The motorcycle further includes a spark generating circuit including a spark plug having a spark gap exposed to the first combustion chamber.
The method further includes the acts of generating a first spark in the first combustion chamber with the first spark plug when the first piston is in a first position, obtaining an ion signal indicative of an ion current across the first spark plug gap, determining if the ion signal indicates knock within the first cylinder, and generating a second spark in the first combustion chamber with the first spark plug when the piston is in a second position and in response to an indication of knock in the first cylinder. The second position is different than the first position.
The invention further provides a software program for determining whether knock is present within a V-twin, air-cooled, motorcycle engine. The software program detects knock by repeatedly sampling a position signal indicative of a position of a first piston in a first cylinder, generating a first spark signal resulting in a first spark being generated in the first cylinder when the piston is in a first position, sampling a knock intensity portion of an ion signal, providing a threshold value, comparing the sample with the threshold value to determine if knock is present within the first cylinder, and generating a second spark signal resulting in a second spark being generated in the first combustion chamber when the piston is in a second position and in response to knock being present in the first cylinder.
Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings.